Compound finFET device including oxidized III-V fin isolator

ABSTRACT

A semiconductor device includes a wafer having a bulk layer and a III-V buffer layer on an upper surface of the bulk layer. The semiconductor device further includes at least one semiconductor fin on the III-V buffer layer. The semiconductor fin includes a III-V channel portion. Either the wafer or the semiconductor fin includes an oxidized III-V portion interposed between the III-V channel portion and the III-V buffer layer to prevent current leakage to the bulk layer.

BACKGROUND

The present invention relates to fin-type field effect transistor(finFET) semiconductor devices, and more specifically, to a III-Vcompound finFET semiconductor device.

The increasing operating speeds and computing power of microelectronicdevices have recently given rise to the need for an increase in thecomplexity and functionality of the semiconductor structures from whichthese devices are fabricated. Integration of compound semiconductormaterials such as, for example, III-V materials, such as galliumarsenide, gallium nitride, indium aluminum arsenide, and/or germaniumwith silicon or silicon-germanium substrate, to form compoundsemiconductor devices having improved material mobility, therebyincreasing the overall functionality and performance of thesemiconductor device.

In particular, heteroepitaxial growth is typically used to fabricatecompound semiconductor devices where lattice-matched substrates are notcommercially available. Performance and, ultimately, the utility ofdevices fabricated using a combination of dissimilar semiconductormaterials, however, depends on the quality of the resulting structure.Namely, a low level of dislocation defects is important in a widevariety of semiconductor devices and processes, because dislocationdefects partition an otherwise monolithic crystal structure andintroduce unwanted and abrupt changes in electrical properties, which,in turn, results in poor material quality and limited performance. Forexample, threading dislocation segments can allow current to leak fromthe semiconductor channel, thereby degrading physical properties of thedevice material and reducing overall performance of the semiconductordevice.

It has long been recognized that gallium arsenide grown on siliconsubstrates achieves increased electron mobility compared to pure siliconmaterial. However, despite the widely recognized potential advantages ofsuch combined structures and substantial efforts to develop them, theirpractical utility has been limited by high defect densities andincreased thread dislocation when growing gallium arsenide layers onsilicon substrates. To control thread dislocation, conventional compoundsemiconductor devices include a deep-well isolation region. Thedeep-well isolation region, however, only reduces the thread dislocationwithout completely eliminating thread dislocation in the compoundsemiconductor device. Consequently, current leakage from thesemiconductor channel still exists.

SUMMARY

According to at least one embodiment of the present invention, asemiconductor device includes a wafer having a bulk layer and a III-Vbuffer layer on an upper surface of the bulk layer. The semiconductordevice further includes at least one semiconductor fin on the III-Vbuffer layer. The semiconductor fin includes a III-V channel portion.Either the wafer or the semiconductor fin includes an oxidized III-Vportion interposed between the III-V channel portion and the III-Vbuffer layer to prevent current leakage to the bulk layer.

According to another embodiment, a method fabricating a semiconductordevice comprises forming a III-V semiconductor stack on an upper surfaceof a wafer. The III-V semiconductor stack includes an intermediate III-Vlayer interposed between an III-V channel layer and a III-V buffer layerformed on the wafer. The method further includes patterning the III-Vchannel layer to form at least one semiconductor fin on the intermediateIII-V layer. The method further includes oxidizing the intermediateIII-V layer to form a III-V oxidation layer that isolates the at leastone semiconductor fin from the III-V buffer layer.

According to still another embodiment, a method of fabricating asemiconductor device comprises forming a III-V semiconductor stack on anupper surface of a wafer. The III-V semiconductor stack including anintermediate III-V layer interposed between an III-V channel layer and aIII-V buffer layer formed on the wafer. The method further includespatterning the III-V channel layer to form at least one semiconductorfin including a buffer III-V portion interposed between an intermediateIII-V portion and a remaining portion of the III-V buffer layer. Themethod further includes selectively oxidizing the intermediate III-Vportion to isolate the at least one semiconductor fin from the III-Vbuffer layer.

Additional features are realized through the techniques of the presentinvention. Other embodiments are described in detail herein and areconsidered a part of the claimed invention. For a better understandingof the invention with the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing features are apparent from the followingdetailed description taken in conjunction with the accompanyingdrawings.

FIGS. 1-8 are a series of diagrams illustrating a process flow offabricating a compound FinFET device including an oxidized III-V finisolator according to a non-limiting embodiment, in which:

FIG. 1 illustrates a starting wafer including a bulk layer and a III-Vsemiconductor stack formed on an upper surface of the bulk layeraccording to a non-limiting embodiment;

FIG. 2 illustrates the wafer of FIG. 1 after patterning the III-Vchannel layer to form one or more semiconductor fins on the uppersurface of the intermediate III-V layer;

FIG. 3 illustrates the wafer of FIG. 2 after forming optional finspacers on opposing sidewalls of the semiconductor fins;

FIG. 4 illustrates the wafer of FIG. 3 following an oxidation process toform an oxidized III-V layer;

FIG. 5 illustrates the wafer of FIG. 4 following a local fin isolationprocess may be to isolate each fin from one another;

FIG. 6 illustrates the wafer of FIG. 5 following an etching process thatexposes a portion of the spacers and an upper surface of the III-Vchannel portion;

FIG. 7 illustrates the wafer of FIG. 6 after performing a secondselective etching process to pull down the fin spacers and expose anupper portion of the III-V channel portion; and

FIG. 8 illustrates the wafer of FIG. 2 after performing the oxidationprocess to convert the intermediate III-V layer into an oxidized III-Vlayer according to another non-limiting embodiment.

FIGS. 9-14 are a series of diagrams illustrating a process flow offabricating a compound FinFET device including an oxidized III-V finisolator according to yet another non-limiting embodiment, in which:

FIG. 9 illustrates a starting wafer including a bulk layer and a III-Vsemiconductor stack formed on an upper surface of the bulk layer, wherethe III-V semiconductor stack includes a III-V interface layerinterposed between the intermediate III-V layer and the III-V channellayer according to a non-limiting embodiment;

FIG. 10 illustrates the wafer of FIG. 9 after patterning the III-Vchannel layer to form one or more semiconductor fins on the uppersurface of the intermediate III-V layer;

FIG. 11 illustrates the wafer of FIG. 10 following the formation ofoptional fin spacers on opposing sidewalls of the semiconductor fins;

FIG. 12 illustrates the wafer of FIG. 11 following an oxidation processto form an oxidized III-V layer;

FIG. 13 illustrates the wafer of FIG. 12 following a selective etchingprocess such that a portion of the spacers and an upper surface of theIII-V channel portion are exposed; and

FIG. 14 illustrates the wafer of FIG. 13 following a second selectiveetching process to pull down the fin spacers and expose an upper portionof the III-V channel portion.

FIGS. 15-19 are a series of diagrams illustrating a process flow offabricating a compound FinFET device including an oxidized III-V finisolator according to still another non-limiting embodiment, in which:

FIG. 15 illustrates a starting wafer including a bulk layer and a III-Vsemiconductor stack formed on an upper surface of the bulk layeraccording to a non-limiting embodiment;

FIG. 16 illustrates the wafer of FIG. 15 after patterning the III-Vchannel layer to form one or more semiconductor fins includingrespective local intermediate III-V fin portions;

FIG. 17 illustrates the wafer of FIG. 16 following a second etchingprocess that punches through the III-V buffer layer while the finhardmasks preserve the fins;

FIG. 18 illustrates the wafer of FIG. 17 following an oxidation processto that converts the localized intermediate III-V portions of each fininto localized oxidized III-V fin portions; and

FIG. 19 illustrates the wafer of FIG. 18 following a local fin isolationprocess to isolate each from one another.

DETAILED DESCRIPTION

Various embodiments described herein provide a compound FinFET deviceincluding an oxidized III-V fin isolator to eliminate thread dislocationand prevent current leakage from the III-V channel of the fins. TheIII-V fin isolator may include an oxidized III-V portion interposedbetween a bulk layer of the wafer and one or more fins. According toanother embodiment, the III-V fin isolator may include an oxidized III-Vportion formed locally with each fin, and interposed between the III-Vchannel and the bulk layer of the wafer. In either case, the oxidizedIII-V layer can serve to prevent current leakage therethrough.Accordingly, the III-fin isolator can prevent any current flowingthrough the III-V channel portions from leaking into the bulk layer,thereby providing a compound FinFET device having improved performance.

With reference now to FIGS. 1-8, a series of diagrams illustrates aprocess flow of fabricating a compound FinFET device including anoxidized III-V fin isolator according to a non-limiting embodiment.Starting with FIG. 1, a starting wafer 100 is illustrated. The wafer 100includes a bulk layer 102, such as a bulk silicon (Si) layer 102 forexample, and a III-V semiconductor stack 104 formed on an upper surfaceof the bulk layer 102. The III-V semiconductor stack 104 includes aplurality of III-V layers 106 a-106 c. The plurality of III-V layers 106a-106 c include a III-V buffer layer 106 a formed on an upper surface ofthe bulk layer 102, an intermediate III-V layer 106 b formed on an uppersurface of the III-V buffer layer 106 a, and a III-V channel layer 106Cformed on an upper surface of the intermediate III-V layer 106 b. Inthis manner, the intermediate III-V layer 106 b is interposed betweenthe III-V channel layer 106 c and the III-V buffer layer 106 a. Anepitaxial growth process may be performed to form each III-V layer 106a-106 c as understood by one of ordinary skill in the art. Although thestack 104 is illustrated as including three III-V layers 106 a-106 c, itshould be appreciated that the number of III-V layers is not limitedthereto.

According to a non-limiting embodiment, each III-V layer 106 a-106 c isformed from a different III-V material. For example, the III-V channellayer 106 c is formed of indium gallium arsenide (InGaAs). The III-Vchannel layer 106 c may contain an amount of indium (In) ranging fromapproximately 20% to approximately 80%, preferably 53%, for example. Theintermediate III-V layer 106 b may be formed of indium aluminum arsenide(InAlAs) and has a thickness ranging from approximately 5 nanometers(nm) to approximately 200 nm, preferably approximately 50 nm, forexample. The III-V buffer layer 106 a may also be formed of InGaAs, butwith a different amount of indium (In). For example, the III-V bufferlayer 106 a may contain an amount of indium (In) ranging from 0% toapproximately 53%, for example, while the III-V channel layer 106 ccontains 0% to approximately 53%, preferably approximately 53% of indium(In), for example.

Referring to FIG. 2, the III-V channel layer 106 c is patterned to formone or more semiconductor fins 108 on the upper surface of theintermediate III-V layer 106 b. The fins 108 can be formed according toa well-known side image transfer (SIT) process, which utilizes a blockhardmask layer (not shown) formed on an upper surface of the III-Vchannel layer 106 c. The block hardmask layer is then patterned todesignate the desired locations of the fins 108, and the pattern istransferred into the III-V channel layer 106 c. The result is one ormore semiconductor fins 108 formed on the intermediate III-V layer 106b. The fins 108 may further include a hardmask 110 that is leftremaining following the fin patterning process as further illustrated inFIG. 2. According to a non-limiting embodiment, the fins 108 have awidth ranging, for example, from approximately 1 nm to approximately 50nm and a height ranging, for example, from approximately 5 nm toapproximately 50 nm.

Referring now to FIG. 3, fin spacers 112 may optionally be formed onopposing sidewalls of the semiconductor fins 108. Various well-knownetching processes may be used to form the fin spacers 112 on the III-Vchannel portion 106 c on the fins 108. For example, a block nitridelayer (not shown) may be deposited on an upper surface of theintermediate III-V layer 106 b to cover the fins 108. Thereafter, areactive ion etch (RIE) process selective to silicon dioxide (SiO2) andIII-V material can be performed to form the fin spacers 112 on thesidewalls of the III-V channel portions 106 c of the fins 108. Thematerials generally used for the hardmask and the spacers 112 includesilicon dioxide and silicon nitride, for example. Depending on theprocessing details and integration schemes, the hardmask may use adifferent material from that for the spacers 112 for reasons such thatthe hardmask need to remain intact while forming/etching the spacerlayer and vice versa.

Turning now to FIG. 4, an oxidation process is applied to the wafer 100.Various chemical oxidation chemistries can be used including, forexample, a wet oxidation process that exposes the intermediate III-Vlayer 106 b to oxygen, for example, thereby forming an oxidized III-Vlayer 114. According to a non-limiting embodiment, the oxidized III-Vlayer 114 is formed having a thickness (i.e., vertical height) ranging,for example, from approximately 1 nm to approximately 50 nm. In the casewhere the intermediate layer 106 b is formed of InAlAs, the oxidationprocess converts the intermediate layer 106 b into an oxidized III-Vlayer 114 comprising indium aluminum oxide (InAlO). The plurality offins 108 are therefore formed on the oxidized III-V layer 114. In thismanner, the oxidized III-V layer 114 isolates the plurality of fins 108from the III-V buffer layer 106 a and the bulk layer 102. The oxidizedIII-V layer 114 further serves to prevent current leakage therethrough.Accordingly, the oxidized III-V layer 114 can serve to prevent anycurrent flowing through the III-V channel portions 106 c from leakinginto the bulk layer 102. The oxidation of InAlAs occurs via a well-knownchemical substitutional process whereby oxygen is substituted for aGroup V element within the semiconductor material. For example, As issubstituted for O through the chemical reaction ofIn_((1-y))Al_(y)As→In_((1-y))Al_(y)O to convert the intermediate layer106 b is formed of InAlAs into an oxidized III-V layer 114 comprisingindium aluminum oxide (InAlO).

Following the oxidation process, a local fin isolation process may beperformed to isolate each fin 108 from one another. Referring forexample to FIG. 5, a block dielectric layer 116 is deposited on an uppersurface of the oxidized III-V layer 114 to cover the fins 108 and thefin hardmasks 110. The block dielectric layer 116 may be formed ofvarious low-k dielectric materials including, for example, silicondioxide (SiO₂). A selective etching process is subsequently performed torecess a portion of the dielectric layer 116 and remove the finhardmasks 110. Accordingly, a portion of the spacers 112 and an uppersurface of the III-V channel portion 106 c are exposed as shown in FIG.6. The etching process may include a reactive ion etch (RIE) process,for example, that is selective to the spacer material (e.g., SiN) andthe III-V channel material (e.g., InGaAs). The selective RIE process mayalso be performed according to a time etch to recess the dielectriclayer 116 to a desired depth.

Turning to FIG. 7, a second selective etching process is performed topull down the fin spacers 112 and expose an upper portion of the III-Vchannel portion 106 c. In this manner, a gate stack (not shown) can beformed to wrap around the upper portion of the III-V channel portion 106c as understood by one of ordinary skill in the art. The second etchingprocess may include a RIE process that is selective to the III-V channelportion material (e.g., InGaAs). In this manner, the recessed dielectriclayer 116 can serve as an etch stop layer, thereby allowing the uppersurface of the fin spacers to be flush with an upper surface of thedielectric layer 116 following the RIE process as further illustrated inFIG. 7.

As previously mentioned above, the fin spacer formation processdescribed with respect to FIG. 3 is optional. Accordingly theintermediate III-V layer 106 b may be converted into the oxidized III-Vlayer 114 as discussed in detail above, but without first requiringformation of fin spacers on sidewalls of the III-V channel portion 106c. In this manner, the fins 108 (excluding fin spacers) are formed onthe upper surface of the oxidized III-V layer 114 as illustrated in FIG.8. Following the oxidization process, the block dielectric layer 116 canbe deposited on the oxidized III-V layer 114 and partially etched toexpose an upper portion of the III-V channel portion as described indetail above. Further, a gate stack (not shown) can be formed to wraparound the exposed III-V channel portions as understood by one ofordinary skill in the art.

With reference now to FIGS. 9-14, a series of diagrams illustrate aprocess flow of fabricating a semiconductor device including an oxidizedIII-V fin isolator according to another non-limiting embodiment. Turningto FIG. 9, a starting wafer 100 includes a bulk layer 102 and a III-Vsemiconductor stack 104 formed on an upper surface of the bulk layer102. The III-V semiconductor stack 104 includes a plurality of III-Vlayers 106 a-106 d. The plurality of III-V layers 106 a-106 d include aIII-V buffer layer 106 a formed on an upper surface of the bulk layer102, an intermediate III-V layer 106 b formed on an upper surface of theIII-V buffer layer 106 a, an III-V interface layer 106 d formed on anupper surface of the intermediate III-V layer 106 b, and a III-V channellayer 106 c formed on an upper surface of the III-V interface layer 106d. In this manner, the intermediate III-V layer 106 b is interposedbetween the III-V interface layer 106 d and the III-V buffer layer 106a, and the III-V interface layer 106 d is interposed between theintermediate III-V layer 106 b and the III-V channel layer 106 c. Anepitaxial growth process may be performed to form each III-V layer 106a-106 d as understood by one of ordinary skill in the art. Although thestack 104 is illustrated as including four III-V layers 106 a-106 d, itshould be appreciated that the number of III-V layers is not limitedthereto.

According to a non-limiting embodiment, each III-V layer 106 a-106 d isformed from a different III-V material. For example, the III-V channellayer 106 c is formed of indium gallium arsenide (InGaAs). The III-Vchannel layer 106 c may contain an amount of indium (In) ranging, forexample, from approximately 20% to approximately 80%, preferablyapproximately 53%, for example. The III-V interface layer may be formedfrom indium phosphide (InP), for example. The intermediate III-V layer106 b may be formed, for example, of indium aluminum arsenide (InAlAs)with a thickness ranging from approximately 5 nm to approximately 200nm, preferably approximately 50 nm. The III-V buffer layer 106 a mayalso be formed of InGaAs, but with a different amount of indium (In).For example, the III-V buffer layer 106 a may contain an amount ofindium (In) ranging, for example, from approximately 0% to approximately53%, for example, while the III-V channel layer 106 c containsapproximately 20% to approximately 80%, preferably approximately 53%, ofindium (In), for example.

Referring to FIG. 10, the III-V channel layer 106 c is patterned to formone or more semiconductor fins 108 on the upper surface of theintermediate III-V layer 106 b. The fins 108 can be formed according toa well-known side image transfer (SIT) process, which utilizes a blockhardmask layer (not shown) formed on an upper surface of the III-Vchannel layer 106 c. The block hardmask layer is then patterned todesignate the desired locations of the fins 108, and the pattern istransferred into the III-V channel layer 106 c and the III-V interfacelayer 106 d. The result is one or more semiconductor fins 108 formed onthe intermediate III-V layer 106 b. Unlike the first embodimentillustrated in FIGS. 1-8, however, the second embodiment differs fromthe first embodiment described above in that each fin 108 includes aIII-V interface portion 106 d interposed between the III-V channelportion 106 c and the III-V buffer layer 106 a. In this manner, theIII-V interface portion 106 d is formed having a wider bandgap than boththe III-V channel portion 106 c and the III-V buffer layer 106 a. Inaddition, the junctions formed therewith have larger barriers forelectron transport from layer 106 d to layer 106 a and layer 106 c andmay serve to prevent any current flowing through the III-V channelportions 106 c from leaking into the bulk layer 102.

The fins 108 may further include a hardmask 110 that is left remainingfollowing the fin patterning process as further illustrated in FIG. 2.According to a non-limiting embodiment, the fins 108 have a widthranging from approximately 1 nm to approximately 50 nm, for example, anda height ranging from approximately 5 nm to approximately 50 nm, forexample.

Referring now to FIG. 11, fin spacers 112 may optionally be formed onopposing sidewalls of the semiconductor fins 108. Various well-knownetching processes may be used to form the fin spacers 112 on the III-Vchannel portion 106 c on the fins 108. For example, a block nitridelayer (not shown) may be deposited on an upper surface of theintermediate III-V layer 106 b to cover the fins 108. Thereafter, areactive ion etch (RIE) process selective to silicon dioxide (SiO₂) andIII-V material can be performed to form the fin spacers 112 on thesidewalls of the III-V channel portions 106 c and III-V interfaceportions 106 c of the fins 108.

Turning now to FIG. 12, an oxidation process is applied to the wafer100. The oxidation process performed is similar to the oxidation processdescribed in detail above with respect to FIG. 4. Various chemicaloxidation chemistries can be used such as a wet oxidation process, forexample, that exposes the intermediate III-V layer 106 b to oxygen, forexample, thereby forming an oxidized III-V layer 114. According to anon-limiting embodiment, the oxidized III-V layer 114 is formed with athickness (i.e., vertical height) ranging, for example, fromapproximately 1 nm to approximately 50 nm. In the case where theintermediate layer 106 b is formed of InAlAs, the oxidation processconverts the intermediate layer 106 b into an oxidized III-V layer 114comprising indium aluminum oxide (InAlO). Unlike the embodimentdescribed with respect to FIGS. 1-8, the III-V interface portion 106 dof the fins 108 is formed directly on the oxidized III-V layer 114. Inthis manner, III-V channel portion 106 c is further isolated from theIII-V buffer layer and bulk substrate layer 102. As discussed above, theoxidized III-V layer 114 further serves to prevent current leakagetherethrough. Accordingly, the oxidized III-V layer 114 can serve toprevent any current flowing through the III-V channel portions 106 cfrom leaking into the bulk layer 102.

Following the oxidation process, a local fin isolation process may beperformed to isolate each fin 108 from one another. Referring forexample to FIG. 13, a block dielectric layer 116 is deposited on anupper surface of the oxidized III-V layer 114 to cover the fins 108 andthe fin hardmasks 110. The block dielectric layer 116 may be formed ofvarious low-k dielectric materials including, for example, silicondioxide (SiO₂). A selective etching process is subsequently performed torecess a portion of the dielectric layer 116 and remove the finhardmasks 110. Accordingly, a portion of the spacers 112 and an uppersurface of the III-V channel portion 106 c are exposed as furtherillustrated in FIG. 13. The etching process may include a reactive ionetch (RIE) process, for example, that is selective to the spacermaterial (e.g., SiN) and the III-V channel material (e.g., InGaAs). Theselective RIE process may also be performed according to a time etch torecess the dielectric layer 116 to a desired depth.

Turning to FIG. 14, a second selective etching process is performed topull down the fin spacers 112 and expose an upper portion of the III-Vchannel portion 106 c. In this manner, a gate stack (not shown) can beformed to wrap around the upper portion of the III-V channel portion 106c as understood by one of ordinary skill in the art. The second etchingprocess may include a RIE process that is selective to the III-V channelportion material (e.g., InGaAs). In this manner, the recessed dielectriclayer 116 can serve as an etch stop layer, thereby allowing the uppersurface of the fin spacers to be flush with an upper surface of thedielectric layer 116 following the RIE process as further illustrated inFIG. 14.

With reference now to FIGS. 15-19, a series of diagrams illustrate aprocess flow of fabricating a semiconductor device including an oxidizedIII-V fin isolator according to yet another non-limiting embodiment.Turning to FIG. 15, a starting wafer 100 includes a bulk layer 102, anda III-V semiconductor stack 104 formed on an upper surface of the bulklayer 102. The III-V semiconductor stack 104 includes a plurality ofIII-V layers 106 a-106 c. The plurality of III-V layers 106 a-106 cinclude a III-V buffer layer 106 a formed on an upper surface of thebulk layer 102, an intermediate III-V layer 106 b formed on an uppersurface of the III-V buffer layer 106 a, and a III-V channel layer 106Cformed on an upper surface of the intermediate III-V layer 106 b. Inthis manner, the intermediate III-V layer 106 b is interposed betweenthe III-V channel layer 106 c and the III-V buffer layer 106 a. Anepitaxial growth process may be performed to form each III-V layer 106a-106 c as understood by one of ordinary skill in the art. Although thestack 104 is illustrated as including three III-V layers 106 a-106 c, itshould be appreciated that the number of III-V layers is not limitedthereto.

According to a non-limiting embodiment, each III-V layer 106 a-106 c isformed from a different III-V material. For example, the III-V channellayer 106 c is formed of indium gallium arsenide (InGaAs). The III-Vchannel layer 106 c may contain an amount of indium (In) ranging, forexample, from approximately 20% to approximately 80%. The intermediateIII-V layer 106 b may be formed of indium aluminum arsenide (InAlAs),for example. The III-V buffer layer 106 a may also be formed of InGaAs,but with a different amount of indium (In). According to a non-limitingembodiment, the III-V buffer layer 106 a may contain an amount of indium(In) ranging from approximately 0% to approximately 53%, for example,while the III-V channel layer 106 c contains approximately 20% toapproximately 80%, preferably approximately 53%, for example, of indium(In).

Referring to FIG. 16, the III-V channel layer 106 c is patterned to formone or more semiconductor fins 108 on the upper surface of the III-Vbuffer layer 106 a. The fins 108 can be formed according to a well-knownside image transfer (SIT) process, which utilizes a block hardmask layer(not shown) formed on an upper surface of the III-V channel layer 106 c.The block hardmask layer is then patterned to designate the desiredlocations of the fins 108, and the pattern is transferred into both theIII-V channel layer 106 c and the intermediate layer 106 b. Unlike thefirst embodiment (FIGS. 1-8) and second embodiment (FIGS. 9-14)discussed above, the third embodiment differs in that each fin 108includes a local intermediate III-V portion 106 b on the III-V bufferlayer 106 a. Each local intermediate III-V portion 106 b has a height(i.e., vertical thickness) ranging, for example, from approximately 5 nmto approximately 200 nm, preferably approximately 50 nm, for example.

The fins 108 may further include a hardmask 110 that is left remainingfollowing the fin patterning process as further illustrated in FIG. 2.According to a non-limiting embodiment, the fins 108 have a widthranging, for example, from approximately 1 nm to approximately 50 nm,and a height ranging for example, from approximately 5 nm toapproximately 50 nm. The SIT process used to form the fins 108 canincluded a selective etching process. For example, a RIE processselective to the hardmask material (e.g., SiN), the III-V channelmaterial (e.g., InGaAs), and the intermediate III-V material (e.g.,InAlAs). In this manner, the III-V buffer layer 106 a is used as an etchstop layer allowing the formation of the fins 108 on the III-V bufferlayer 106 a.

Turing to FIG. 17, the wafer 100 is illustrated following a secondetching process. The second etching process punches through the III-Vbuffer layer 106 a while the fin hardmasks 110 preserve the fins 108. Inthis manner, III-V buffer portions 107 are interposed between the localintermediate III-V portions 106 b and the recessed III-V buffer layer106 a. The III-V buffer portions 107 have a lateral width (e.g.,horizontal thickness) that does not exceed the width of the localintermediate III-V layers 106 b. The second etching process may includea timed RIE process that is applied to the III-V buffer layer 106 a. Thetime at which to apply the etching process can be chosen to etch theIII-V buffer layer 106 a to a particular depth in order to achieve adesired height (i.e., vertical thickness) of the intermediate III-Vportions 107.

Turning now to FIG. 18, an oxidation process is applied to the wafer100. The oxidation process in this embodiment is similar to theoxidation process described in detail above with respect to FIGS. 4 and12. Namely, various chemical oxidation chemistries can be usedincluding, for example, a wet oxidation process that exposes theintermediate III-V layer 106 b to oxygen, for example. In this case,however, each fin 108 is formed with a local oxidized III-V portion 114,as opposed to each fin 108 being formed directly on a single oxidizedIII-V layer 114 that is common to all the fins 108.

According to a non-limiting embodiment, the oxidized III-V layer 114 isformed with a thickness (i.e., vertical height) ranging for example,from approximately 1 nm to approximately 50 nm. In the case where theintermediate layer 106 b is formed of InAlAs, the oxidation processconverts the intermediate portions 106 b into an oxidized III-V portions114 comprising indium aluminum oxide (InAlO). In this manner, the III-Vchannel portion 106 c is isolated from the III-V buffer layer 106 a andbulk substrate layer 102. As discussed above, the oxidized III-Vportions 114 further serve to prevent current leakage therethrough.Accordingly, the oxidized III-V portions 114 can serve to prevent anycurrent flowing through the III-V channel portions 106 c from leakinginto the bulk layer 102.

Referring to FIG. 19, a local fin isolation process may be performed toisolate each from one another following the oxidation process. Asdiscussed above, a dielectric layer 116 can be deposited on an uppersurface of the oxidized III-V layer 114 to cover the fins 108 and thefin hardmasks 110. The block dielectric layer may be formed of variouslow-k dielectric materials including, for example, silicon dioxide(SiO₂).

A selective etching process is performed to pull down dielectric layer116 and expose an upper portion of the III-V channel portion 106 c asfurther illustrated in FIG. 19. The etching process may include a RIEprocess that is selective to the III-V channel portion material (e.g.,InGaAs). Accordingly, a gate stack (not shown) can be formed to wraparound the upper portion of the III-V channel portion 106 c asunderstood by one of ordinary skill in the art. Although not illustratedin FIG. 15-19, it should be appreciated that spacers can be formed onsidewalls of the fins 108 as discussed above with respect to FIGS. 3 and11.

Various embodiments described in detail above provide a compound FinFETdevice including an II-V oxidation layer, i.e., oxidized III-V finisolator to reduce thread dislocation and prevent current leakage fromthe III-V channel of the fins. The III-V fin isolator may include anoxidized III-V interposed between a bulk layer of the wafer and one ormore fins. According to another embodiment, the oxidized III-V finisolator may include an oxidized III-V portion formed locally with eachfin, and interposed between the III-V channel and the bulk layer of thewafer. In either case, the oxidized III-V isolator can serve to preventcurrent leakage therethrough. Accordingly, the oxidized III-fin isolatorcan prevent any current flowing through the III-V channel portions fromleaking into the bulk layer, thereby providing a compound FinFET devicehaving improved performance.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of onemore other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the inventive teachings and the practical application, andto enable others of ordinary skill in the art to understand theinvention for various embodiments with various modifications as aresuited to the particular use contemplated.

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the operations described thereinwithout departing from the spirit of the invention. For instance, theoperations may be performed in a differing order or operations may beadded, deleted or modified. All of these variations are considered apart of the claimed invention.

While various embodiments have been described, it will be understoodthat those skilled in the art, both now and in the future, may makevarious modifications which fall within the scope of the claims whichfollow. These claims should be construed to maintain the properprotection for the invention first described.

What is claimed is:
 1. A semiconductor device comprising: a waferextending along a first direction to define a length, a second directionopposite the first direction to define a width, and a third directionopposite the first and second directions to define a height, the waferincluding a bulk layer and a III-V buffer layer on an upper surface ofthe bulk layer, the III-V buffer layer comprising indium (In) andextending continuously along the entire length of the wafer; and atleast one semiconductor fin directly on an upper surface of the III-Vbuffer layer, the at least one semiconductor fin including a III-Vchannel portion comprising indium (In), wherein one of the wafer or theat least one semiconductor fin includes an oxidized III-V portiondirectly on an upper surface of the III-V buffer layer such that theoxidized III-V portion is interposed between the III-V channel portionand the III-V buffer layer configured to prevent current leakage fromthe III-V channel portion to the bulk layer.
 2. The semiconductor deviceof claim 1, wherein the III-V buffer layer extends approximately a fullwidth of the wafer.
 3. The semiconductor device of claim 2, wherein thewafer includes the oxidized III-V portion on the III-V buffer layer, theoxidized portion extending approximately the full width of the wafer. 4.The semiconductor device of claim 3, wherein the at least onesemiconductor film includes a III-V interface portion interposed betweenthe III-V channel portion and the oxidized III-V portion.
 5. Thesemiconductor device of claim 1, wherein the oxidized III-V portion is alocalized oxidized portion of the at least one semiconductor fin, thelocalized oxidized portion having a first width that does not exceed asecond width of the III-V channel portion, wherein the at least onesemiconductor fin includes a III-V buffer portion interposed between thelocalized oxidized III-V portion and the III-V buffer layer, and whereinthe III-V buffer portion has a width less than the III-V buffer portion.